Information recording/reproducing apparatus including a recording controller which operates based on prepit detection

ABSTRACT

An information recording/reproducing apparatus which is capable of recording information data even if prepits cannot be correctly read from a recording medium. Prepits are detected from a read signal retrieved from a recording medium to generate a prepit detection signal, and a block signal indicative of a recording timing is generated based on the prepit detection signal. In this event, when the prepit detection signal is normal, an information signal is recorded on the recording medium at a recording timing in accordance with the block signal. On the other hand, when the prepit detection signal is defective, the information signal is recorded on the recording medium at a recording timing in accordance with an auxiliary block signal having the same period as a block length, and a fixed phase.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information recording/reproducingapparatus for recording and reproducing information data on and from arecording medium.

2. Description of Related Art

At present, CD-R, CD-RW, DVD-R, DVD-RW, DVD-RAM and the like are knownas optical recording discs on which information data can be written.Further, disc recorders for writing information data on such recordingdiscs have been commercially available.

FIG. 1 is a diagram generally showing areas which comprise a DVD-RW as arecording disc.

As shown in FIG. 1, the DVD-RW has a data structure comprised, from theinner periphery to the outer periphery of the disc, of PCA (PowerCalibration Area), RMA (Recording Management Area), a lead-in area,data, and a lead-out area. PCA is an area for attempting a write fordetermining the recording power for a laser beam. RMA is an area intowhich management information related to recording is written. Thelead-in area is partially formed with an emboss portion. The embossportion includes phase pits previously formed on the disc, andinformation related to copy protection and the like may be recorded inthe emboss portion.

FIG. 2 is a diagram showing a portion of a recording surface of therecording disc.

As shown in FIG. 2, a disc substrate 101 is spirally or concentricallyformed with convex groove tracks 103, which are to be formed withinformation pits Pt that carry information data, and concave land tracks102. The groove tracks 103 and land tracks 102 are alternately formed.Further, between mutually adjacent groove tracks 103, a plurality ofLPPs (land prepits) 104 are formed. The LPPs 104 are previously providedon the land tracks 102 for knowing a recording timing and an addresswhen a disc recorder records information data.

For recording information data in an unrecorded region AN, in which noinformation pits Pt have been formed, as shown in FIG. 2, the discrecorder first reads the LPPs 104 from the recording disc to recognizean address on the recording disc. Then, the disc recorder formsinformation pits Pt which carry information data on the groove tracks103, corresponding to the recognized address.

However, troubles as follows are experienced when information data isrecorded on an unrecorded track adjacent to a recorded region.

Specifically, when a recorded region exists outside a recording track onwhich information data is to be recorded, the disc recorder maysometimes fail to correctly read the LPPs 104 existing between arecorded region A_(R) and an unrecorded region A_(N) due to theinfluence of information pits Pt formed on the groove track 103indicated by an outlined arrow in FIG. 2. In this event, the discrecorder cannot identify a recording start timing on the recording disc,resulting in a trouble which involves the inability of the disc recorderto record information data on the grove track 103 indicated by a solidblack arrow. Further, a similar problem arises in the emboss portion orPCA as well that the LPPs 104 are incorrectly read so that the discrecorder cannot record in these areas.

Unlike the foregoing case, the disc recorder may experience difficultiesin reading LPPs 104 at particular locations on some discs due to theinfluence of variations in quality, in which case the LPPs 104 areincorrectly read so that the disc recorder fails to record on the disc.

OBJECT AND SUMMARY OF THE INVENTION

The present invention has been made to solve the problems mentionedabove, and it is an object of the invention to provide an informationrecording/reproducing apparatus which is capable of recordinginformation data even if the apparatus experiences difficulties incorrectly reading land prepits.

An information recording/reproducing apparatus according to the presentinvention is configured to record an information signal in units ofpredetermined block length on a recording medium which has previouslybeen formed with prepits associated with recording timings. Theinformation recording/reproducing apparatus includes a reader forreading recorded information from the recording medium to generate aread signal, a prepit detector for detecting the prepits from the readsignal to generate a prepit detection signal, a recording timing signaldetector for detecting a block signal indicative of a recording timingfor the information signal based on the prepit detection signal, anauxiliary recording timing signal generator for generating a pulsesignal having the same period as the block length, and outputting thepulse signal as an auxiliary block signal, and a recording controllerfor recording the information signal on the recording medium at arecording timing in accordance with the block signal when the prepitdetection signal is normal, and for recording the information signal onthe recording medium at a recording timing in accordance with theauxiliary block signal when the prepit detection signal is defective.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are diagrams showing the data structure and theconfiguration on a recording surface of a recording disc on whichinformation data can be written;

FIG. 3 is a block diagram illustrating the configuration of a discrecorder as an information recording/reproducing apparatus according tothe present invention;

FIG. 4 is a diagram showing waveforms associated with the operation of apre-address detector circuit 22 and a recording timing detector circuit23;

FIG. 5 is a block diagram illustrating the internal configuration of thepre-address detector circuit 22 and recording timing detector circuit23;

FIG. 6 is a flow chart illustrating a first forced lock control routine;and

FIG. 7 is a flow chart illustrating a second forced lock controlroutine.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 3 is a block diagram illustrating the configuration of a discrecorder as an information recording/reproducing apparatus according tothe present invention.

In FIG. 3, a recording signal processing circuit 1 performs desiredrecording modulation processing on Information data, which is to berecorded, to produce a modulated recording signal RM which is suppliedto a recording/reproducing head 2 in response to a variety of recordinginstruction signals supplied from a system control circuit 100. Therecording/reproducing head 2 irradiates a recording surface of awritable recording disc such as CD-R, CD-RW, DVD-R, or DVD-RW with awriting light beam in accordance with the modulated recording signal RM.Here, the description is made on a DVD-RW taken as representative of therecording disc 3. As illustrated in FIG. 2, the recording disc 3 isspirally or concentrically formed on a recording surface thereofalternately with groove tracks 103 and land tracks 102. Further,physical addresses on the recording disc 3 and a plurality of LPPs (landprepits) 104 are formed between mutually adjacent groove tracks 103. TheLPPs 104 are previously formed on the land tracks 102 at locations atwhich synchronization timings are established, and at locations at whichpre-data are carried.

Here, as a writing light beam is irradiated to the recording surface ofthe recording disc 3 as described above, information pits Ptcorresponding to the modulated recording signal RM are formed on thegroove tracks 103 as illustrated in FIG. 2. One code block of themodulated recording signal RM is recorded in 16 sectors on the recordingdisc 3 as shown in FIG. 4. In this event, one sector is comprised of 26frames as shown in FIG. 4.

A recording/reproducing head 2 receives reflected light when a readinglight beam is irradiated on a groove track 103 formed on the recordingsurface of the recording disc 3, photoelectrically transduces thereflected light into a read signal RS which is output. A slider unit 4moves the recording/reproducing head 2 in a radial direction of therecording disc 3. An information data reproducing circuit 5 binarizesthe read signal RS, and performs desired demodulation processing on thebinarized signal to reproduce information data which is output asreproduced information data. An information data address extractingcircuit 6 extracts the address of the reproduced information datagenerated in the information data reproducing circuit 5 based on theread signal RS, and supplies the address to a system control circuit 100as information data address AD₁. An error generator circuit 7 generatesa focus error signal FE based on the read signal RS for adjusting thefocal points of the writing and reading light beams irradiated by therecording/reproducing head 2 to the recording surface of the recordingdisc 3, and supplies the focus error signal FE to a servo controlcircuit 8. The error generator circuit 7 further generates a trackingerror signal TE based on the read signal RS for tracking the light beamon the groove track 103 on the recording disc 3, and supplies thetracking error signal TE to the servo control circuit 8. The servocontrol circuit 8 generates a focusing drive signal FD in accordancewith the focus error signal FE, and supplies the focusing drive signalFD to the recording/reproducing head 2 through a driver 9. In this way,a focusing actuator (not shown) equipped in the recording/reproducinghead 2 adjusts the focal points of the writing and reading light beamsby a portion corresponding to the focusing drive signal FD. The servocontrol circuit 8 also generates a tracking drive signal TD based on thetracking error signal TE, and supplies the tracking drive signal TD tothe recording/reproducing head 2 through a driver 10. In this way, atracking actuator (not shown) equipped in the recording/reproducing head2 offsets a position irradiated with the reading and writing light beamsby a portion corresponding to a drive current generated by the trackingdrive signal TD in the radial direction of the recording disc 3. Theservo control circuit 8 further generates a slider drive signal SD inaccordance with the tracking error signal TE, and supplies the sliderdrive signal SD to the slider unit 4 through a driver 11. In this way,the slider unit 4 moves the recording/reproducing head 2 in accordancewith the slider drive signal SD in the radial direction of the disc.

An LPP (land prepit) detector circuit 12 generates an LPP detectionsignal LPD which exhibits a pulsatile change in level as shown in FIG. 4each time it detects a signal in response to the LPPs 104, asillustrated in FIG. 2, read from the read signal RS. In this event, whenthe LPPs 104 as illustrated in FIG. 2 are normally read by therecording/reproducing head 2, the LPP detection signal LPD includesperiodic pulses P_(SYNC) which appear at a period T as shown in FIG. 4,and pre-data pulses P_(DP) which carry pre-data.

An LPP (land prepit) defect determining circuit 21 determines whether ornot the periodic pulses P_(SYNC) as shown in FIG. 4 appear at the periodT in the LPP detection signal LPD to determine defectively read LPPs 104as illustrated in FIG. 2. Specifically, the LPP defect determiningcircuit 21 supplies the system control circuit 100 with a defectdetermination signal ER at logical level “0” indicative of non-defectivewhen the periodic pulses P_(SYNC) appear at the period T in the LPPdetection signal LPD. On the other hand, when the periodic pulsesP_(SYNC) do not appear at the period T in the LPP detection signal LPD,an LPP detection defect determining circuit 208 supplies the systemcontrol circuit 100 with the defect determination signal ER at logicallevel “1” indicative of defective. In other words, when therecording/reproducing head 2 fails to correctly read the LPP 104 asillustrated in FIG. 2, the period of the synchronization pulses P_(SYNC)in the LPP detection signal LPD does not match the period T, so that theLPP defect determining circuit 21 determines this state as defective.

Alternatively, the following approach may be employed as the defectiveread determining approach.

The pre-data pulses P_(PD) included in the LPP detection signal LPD asshown in FIG. 4 are decoded to produce a sector address. The sectoraddress takes a value from “0” to “15” which is incremented every sectoras shown in FIG. 4. A defectively read LPP can be determined bydetermining whether or not the sector address is regularly generated.While the sector address can be decoded even if all LPPs cannot read, apredetermined amount of correctly read LPP is required. Therefore, thecorrectly read sector address indicates that the LPPs are beingsatisfactorily read to a certain degree or more. The defective readdetermination based on the sector address can be implemented in asimilar configuration to an address decoder 201 and a block signalgenerator circuit 202, later described. In this event, the blockgenerator circuit senses whether or not sector addresses are regularlyread, and outputs a logical level “0” indicative of non-defective as thedefect determination signal ER, when the sector addresses are regularlyread. On the other hand, when the sector addresses are not regularlyread, the block generator circuit outputs the defect determinationsignal ER at logical level “1” indicative of defective.

A pre-address detector circuit 22 detects a pre-address, which has beenpreviously set on the recording disc 3, based on the LPP detectionsignal LPD, and supplies the system control circuit 100 with thedetected pre-address as a pre-address AD_(P).

A recording timing detector circuit 23 generates a timing signalindicative of a position at which each code block exists in a modulatedrecording signal RM, based on the LPP detection signal LPD, and suppliesthe system control circuit 100 with the timing signal as a block signalBLK.

FIG. 5 Is a block diagram illustrating the internal configuration of thepre-address detector circuit 22 and recording timing detector circuit23.

In FIG. 5, an address decoder 201 decodes a pre-data pulse P_(PD)included in an LPP detection signal LPD as shown in FIG. 4 to generate asector address. The sector address takes a value from “0” to “15” whichis incremented every sector, as shown in FIG. 4.

A block signal generator circuit 202 confirms whether or not the sectoraddress regularly increments by one in the range of “0” to “15,” andoutputs a block signal BLK_(N) at a timing of sector address “0” whenthe sector address regularly increments. Therefore, the block signalBLK_(N) generates a pulsatile change in level at the timing synchronizedin phase to each code block in the modulated recording signal RM, asshown in FIG. 4. A PLL (phase locked loop) circuit 203 is supplied witha reference clock signal, which has a sufficiently short period ascompared with the synchronization pulse P_(SYNC), by a clock generatorcircuit, not shown. The PLL circuit 203 synchronizes the reference clocksignal to the synchronization pulse P_(SYNC) in the LPP detection signalLPD as shown in FIG. 4 to generate a clock pulse signal CK which issupplied to a frequency division counter 204. The frequency divisioncounter 204 counts the number of clock pulses in the clock pulse signalCK, and generates an auxiliary block signal BLK_(S), in which pulsesappear as shown in FIG. 4, each time the total number of counted clockpulses reaches a predetermined number. In other words, the frequencydivision counter 204 generates the clock pulse signal CK, which isgenerated by dividing the clock pulse signal by a predetermined number,as the auxiliary block signal BLK_(S). In this way, even if the LPP 104is difficult to read and therefore the synchronization pulses P_(SYNC)sometimes drop, PLL works well, so that the auxiliary block signalBLK_(S) can be output every code block, as shown in FIG. 4. In thisevent, the auxiliary block signal BLK_(S) has the same period as theperiod of one code block of the modulated recording signal RM, as shownin FIG. 4.

The PLL circuit 203 synchronizes the phase based on the detection of theLPPs 104 to generate the clock pulse CK. Alternatively, the recordingtrack meanders at a predetermined period as illustrated in FIG. 2, sothat the clock pulse signal CK may be generated by synchronizing thephase based on a wobble signal generated by detecting the meanderingpattern and then synchronizing the phase based on the LPPS. Since thewobble signal has a shorter period than the LPPS, the PLL can beaccurately applied as compared with the LPP, even if some informationdrops. Additionally, the accuracy can be improved by applying the PLL intwo stages. A selector 205 selects the block signal BLK_(N) from theblock signal BLK_(N) and auxiliary block signal BLK_(S) when it issupplied with a forced lock signal LOCK at logical level “0” from thesystem control circuit 100, and supplies the selected one to the systemcontrol circuit 100 as the final block signal BLK. On the other hand,when the forced lock signal LOCK is at logical level “1” indicative of aforced lock instruction, the selector 205 selects the auxiliary blocksignal BLK_(S) which is supplied to the system control circuit 100 asthe block signal BLK. In other words, the selector 205 normally outputsthe block signal BLk_(N) which is generated based on the synchronizationpulse P_(SYNC) existing in the LPP detection signal LPD as shown in FIG.4 as the block signal BLK indicative of a recording timing. However,when the selector 205 is supplied with the forced lock instruction fromthe system control circuit 100, the selector 205 outputs the auxiliaryblock signal BLK_(S) generated in a self-oscillation circuit comprisedof the PLL circuit 203 and frequency division counter 204 as the blocksignal BLK indicative of a recording timing.

A pre-data bit generator circuit 206 generates a pre-data bit PD_(bit)which is at logical level “1” when a pre-data pulse P_(PD) as shown inFIG. 4 exists immediately after a synchronization pulse P_(SYNC)included in an LPP detection signal LPD, and at logical level “0” whenno such pre-data pulse P_(PD) exists, and supplies the pre-data bitPD_(bit) to a pre-address extracting circuit 207. The pre-addressextracting circuit 207 retrieves every one code block of the pre-databits PD_(bit), i.e., every 208 bits, extracts predetermined 24 bitswithin the sequence of bits, and supplies the extracted 24 bits to thesystem control circuit 100 as a pre-address AD_(P).

For additionally writing information data on the recording disc 3, thesystem control circuit 100 moves the recording/reproducing head 2 at aposition predetermined tracks, for example, ten code blocks before arecording start location within an unrecorded region A_(N) of therecording disc 3 as illustrated in FIG. 2, and supplies the servocontrol circuit 8 with an instruction signal for starting a readoperation from that position. In response to the instruction, therecording/reproducing head 2 first starts reading information within theunrecorded region A_(N). In this event, in a read signal RS output fromthe recording/reproducing head 2, pulses appear in response to read LPP104.

Here, the system control circuit 100 proceeds to the execution of afirst forced lock control routine as illustrated in FIG. 6.

In FIG. 6, the system control circuit 100 first retrieves a defectdetermination signal ER supplied from the LPP defect determining circuit21 (step S1). Next, the system control circuit 100 determines whether ornot the defect determination signal ER is at logical level “1”indicative of defectively read LPPs (step S2). If the system controlcircuit 100 determines at step S2 that the defect determining signal ERis not at logical level “1”, i.e., determines that the LPPs are beingnormally read, the system control circuit 100 supplies the recordingtiming detector circuit 23 with a forced lock signal LOCK at logicallevel “0” (step S3). In response to the forced lock signal LOCK atlogical level “0” supplied thereto, the recording timing detectorcircuit 23 sends a block signal BLK_(N) generated based on asynchronization pulse P_(SYNC), which exists in an LPP detection signalLPD, to the system control circuit 100 as a block signal BLK.

On the other hand, if the system control circuit 100 determines at stepS2 that the defect determination signal ER is at logical level “1”indicative of defectively read LPPs, the system control circuit 100proceeds to the execution of an LPP read retry processing subroutine(step S4).

In the LPP read retry processing subroutine, the system control circuit100 moves the recording/reproducing head 2 backward by 10 code blocksfrom a desired recording start position, and again reads the LPPs 104 ina manner similar to the aforementioned operation to determine thereading state. In other words, the system control circuit 100 retrievesthe defect determination signal ER supplied from the LPP defectdetermining circuit 21 (step S4). Next, the system control circuit 100determines whether or not the defect determination signal ER is atlogical level “1,” i.e., whether or not the LPPs are defectively read(step S5). If the system control circuit 100 determines at step S5 thatthe defect determination signal ER is at logical level “0,” i.e.,determines that the LPPs are normally read, the system control circuit100 proceeds to the execution of the aforementioned step S3. On theother hand, if the system control circuit determines that the defectdetermination signal ER is at logical level “1,” i.e., determines thatthe LPPs are defectively read, the system control circuit 100 suppliesthe slider unit 4 with a slider drive signal SD for moving therecording/reproducing head 2 backward by ten code blocks from a desiredrecording start position (step S6). Here, after therecording/reproducing head 2 has been moved, the system control circuit100 again starts reading the LPP 104 from that position, and suppliesthe recording timing detector circuit 23 with the forced lock signalLOCK at logical level “1” (step S7). In response to the forced locksignal LOCK at logical level “1” supplied thereto, the recording timingdetector circuit 23 sends an auxiliary block signal BLK_(S), generatedin the self-oscillation circuit comprised of the PLL circuit 203 andfrequency division counter 204, to the system control circuit 100 as theblock signal BLK. Stated another way, in this event, the system controlcircuit 100 is supplied with the auxiliary block signal BLK_(S) with afixed phase as a block signal indicative of a recording timing.

After executing the foregoing step S3 or S8, the system control circuit100 exits the first forced lock control routine, and proceeds to theexecution of a recording control routine. In the execution of herecording control routine, the system control circuit 100 supplies therecording signal processing circuit 1 with a recording instructionsignal for recording a modulated recording signal RM at a position onthe recording disc 3 indicated by the pre-address AD_(P) at therecording timing of the block signal BLK supplied from the recordingtiming detector circuit 23. In this way, information pits Pt accordingto the modulated recording signal RM are recorded on a groove track 103on the recording disc 3. In this recording operation, the first forcedlock control routine as illustrated in FIG. 6 is also executedrepeatedly at predetermined intervals.

Thus, according to the execution of the first forced lock controlroutine, even if the LPPs 104 are defectively read during the recordingoperation so that the block signal BLK_(N) is not detected based on theLPP detection signal LPD, the recording timing can be provided by theauxiliary block signal BLK_(S)in place of the block signal BLK_(N).

While in the foregoing embodiment, the retry for the defective LPP readdetermination is performed only once, the retry may be performed aplurality of times. Alternatively, the routine may proceed to theprocessing at step S6 without executing the LPP read retry and defectdetermination at steps S4 and S5.

Since a DVD-RW permits information to be recorded on the outerperipheral side away from the unrecorded region on the disc, informationmay be recorded on the inner peripheral side of the recorded region asillustrated in FIG. 2 in some situation. As an exemplary case where arecorded region exists on the outer peripheral side of a position atwhich information is recorded, recording in the PCA is contemplated. ThePCA, which is a area for recording a calibration signal for therecording power of the recording/reproducing head 2, is defined to beused from the outer peripheral side to the inner peripheral side of thedisc for every predetermined area. In this event, since the calibrationsignal may be recorded with very high power in some cases, therecording/reproducing head 2 will experience difficulties in readingLPPs 104.

Thus, for additionally writing information data on the inner peripheralside of a recorded region, a forced lock is essentially applied withoutthe defect determination at step S2.

FIG. 7 is a flow chart illustrating a second forced lock control routinewhich is implemented in view of the foregoing aspect.

In FIG. 7, the system control circuit 100 first determines whether ornot defective reading of LPPs is expected around a position at whichinformation data is additionally written, or a region a predeterminedcode blocks (for example, five code blocks) before that position, i.e.,whether or not a recorded region exists near that position (step S61).For making this determination, the recording/reproducing head 2previously scans a region including the surroundings of the recordingposition to check whether or not a recorded region exists beforestarting the recording, and stores addresses indicative of the recordedregion, if any, in a memory. Then, the system control circuit 100 oranother microcomputer (not shown) references the contents stored in thememory to determine whether or not defective reading of LPPs is expectedat the position, i.e., whether or not a recorded region exists at theposition.

When determining at step S61 that a recorded region exists at theaforementioned position, the system control circuit 100 supplies therecording timing detector circuit 23 with a forced lock signal LOCK atlogical level “1” (step S62). In response to the forced lock signal LOCKat logical level “1” supplied thereto, the recording timing detectorcircuit 23 sends an auxiliary block signal BLK_(S) generated in theself-oscillation circuit comprised of the PLL circuit 203 and frequencydivision counter 204 to the system control circuit 100 as a block signalBLK. In this event, the system control circuit 100 controls therecording signal processing circuit 1 in order to start recording amodulated recording signal RM on the recording disc 3 at a recordingtiming based on the auxiliary block signal BLK_(S) which has beenapplied with the forced lock (step S63). On the other hand, whendetermining at step S62 that no recorded region exists, the systemcontrol circuit 100 proceeds to the execution of the first forced lockcontrol routine as illustrated in FIG. 6.

When calibration is performed in te PCA, a recording operation isperformed in a forced lock state created at the aforementioned steps S62and S63. Specifically, since a recorded region exists outside the PCA,the PCA satisfies the condition at step 61 in FIG. 7 of a position atwhich defective reading of LPPs is expected.

Also, for recording in a region adjoining the outer peripheral side ofthe emboss portion, recording preparation is required for tracing theemboss portion. Due to the structure of the emboss portion in which LPPscan be read but information cannot be written. LPPs in the embossportion are more difficult to read as compared with LPPs in otherunrecorded regions. For this reason, the system control circuit 100 alsoperforms a recording operation in a forced lock state when informationis recorded in such a region which requires the recording preparationfor tracking the emboss portion. Specifically, since the emboss portionfalls under the definition of a position at which defective reading ofLPPs is expected, a recording operation is performed in the forced lockstate created at the aforementioned steps S62 and S63.

While in the foregoing embodiment, the operation of the presentinvention has been described in connection with an informationrecording/reproducing apparatus, taken as an example, for recording andreproducing a DVD-RW, the present invention can be applied to a varietyof information recording/reproducing apparatuses for recording andreproducing other recording media.

As described above in detail, in the present invention, when LPPs aredefectively read during a recording operation, a block signal generatedbased on the LPPs is replaced with a block signal having the same periodas this block signal but a fixed phase for use as a recording timingsignal.

Therefore, according to the present invention, information data can bewritten into a location on a recording medium which is susceptible todefective reading of LPPs.

This application is based on Japanese Patent Application No. 2001-6971which is hereby incorporated by reference.

1. An information recording/reproducing apparatus for recording aninformation signal in units of predetermined block length on a recordingmedium which has previously been formed with prepits associated withrecording timings, said apparatus comprising: a reader for readingrecorded information from said recording medium to generate a readsignal; a prepit detector for detecting the prepits from the read signalto generate a prepit detection signal; a recording timing signaldetector for detecting a block signal indicative of a recording timingfor the information signal based on the prepit detection signal; anauxiliary recording timing signal generator for generating a pulsesignal having the same period as the block length by using a referenceclock signal, and outputting the pulse signal as an auxiliary blocksignal; and a recording controller for recording the information signalon said recording medium at a recording timing in accordance with theblock signal when the prepit detection signal is normal, and forrecording the information signal on said recording medium at a recordingtiming in accordance with the auxiliary block signal when the prepitdetection signal is defective.
 2. An information recording/reproducingapparatus for recording an information signal in units of predeterminedblock length on a recording medium which has previously been formed withprepits associated with recording timings, said apparatus comprising: areader for reading recorded information from said recording medium togenerate a read signal; a prepit detector for detecting the prepits fromthe read signal to generate a prepit detection signal; a recordingtiming signal detector for detecting a block signal indicative of arecording timing for the information signal based on the prepitdetection signal; an auxiliary recording timing signal generator forgenerating a pulse signal having the same period as the block length,and outputting the pulse signal as an auxiliary block signal; arecording controller for recording the information signal on saidrecording medium at a recording timing in accordance with the blocksignal when the prepit detection signal is normal, and for recording theinformation signal on said recording medium at a recording timing inaccordance with the auxiliary block signal when the prepit detectionsignal is defective; and a prepit defect determining part fordetermining whether or not the prepit detection signal is defective. 3.An information recording/reproducing apparatus for recording aninformation signal in units of predetermined block length on a recordingmedium which has previously been formed with prepits associated withrecording timings, said apparatus comprising: a reader for readingrecorded information from said recording medium to generate a readsignal; a prepit detector for detecting the prepits from the read signalto generate a prepit detection signal; a recording timing signaldetector for detecting a block signal indicative of a recording timingfor the information signal based on the prepit detection signal; anauxiliary recording timing signal generator for generating a pulsesignal having the same period as the block length, and outputting thepulse signal as an auxiliary block signal; and a recording controllerfor recording the information signal on said recording medium at arecording timing in accordance with the block signal when the prepitdetection signal is normal, and for recording the information signal onsaid recording medium at a recording timing in accordance with theauxiliary block signal when the prepit detection signal is defective,wherein said auxiliary recording timing signal generator comprises: aPLL circuit for generating a clock signal at a predetermined frequency,synchronized in phase to the prepit detection signal; and a frequencydivision counter for dividing the clock signal by a predetermined numberto generate a divided clock signal as the auxiliary block signal.
 4. Aninformation recording/reproducing apparatus for recording an informationsignal in units of predetermined block length on a recording mediumwhich has previously been formed with prepits associated with recordingtimings, said apparatus comprising: a reader for reading recordedinformation from said recording medium to generate a read signal; aprepit detector for detecting the prepits from the read signal togenerate a prepit detection signal; a recording timing signal detectorfor detecting a block signal indicative of a recording timing for theinformation signal based on the prepit detection signal; an auxiliaryrecording timing signal generator for generating a pulse signal havingthe same period as the block length, and outputting the pulse signal asan auxiliary block signal; and a recording controller for recording theinformation signal on said recording medium at a recording timing inaccordance with the block signal when the prepit detection signal isnormal, and for recording the information signal on said recordingmedium at a recording timing in accordance with the auxiliary blocksignal when the prepit detection signal is defective, wherein saidrecording controller records the information signal on said recordingmedium at a recording timing in accordance with the auxiliary blocksignal when the information signal is recorded on an unrecorded trackadjacent to a recorded region on said recording medium.
 5. Aninformation recording/reproducing apparatus for recording an informationsignal in units of predetermined block length on a recording mediumwhich has previously been formed with prepits associated with recordingtimings, said apparatus comprising: a reader for reading recordedinformation from said recording medium to generate a read signal; aprepit detector for detecting the prepits from the read signal togenerate a prepit detection signal; a recording timing signal detectorfor detecting a block signal indicative of a recording timing for theinformation signal based on the prepit detection signal; an auxiliaryrecording timing signal generator for generating a pulse signal havingthe same period as the block length, and outputting the pulse signal asan auxiliary block signal; and a recording controller for recording theinformation signal on said recording medium at a recording timing inaccordance with the block signal when the prepit detection signal isnormal, and for recording the information signal on said recordingmedium at a recording timing in accordance with the auxiliary blocksignal when the prepit detection signal is defective, wherein: saidrecording medium is a recording disc which is previously provided withan OPC area for performing a trial write in determining light power of arecording laser beam, and an emboss portion for recording informationrelated to copy protection, and said recording controller records theOPC area or the emboss portion at a recording timing in accordance withthe auxiliary block signal.